The present invention relates to a zoom lens system that is suitable for use with compact cameras which have a smaller constraint on back focus than single-lens reflex cameras.
Two-group zoom lens systems of the type contemplated by the present invention that permit zoom ratios of about 2 and which are adapted for use with compact cameras have been known and available in various compositions. One example is a system that consists of about eight lens elements and which includes only spherical surfaces (see Japanese Patent Laid-Open Publication No. SHO 62-264019), while another example is a system that consists of four lens elements and which employs many aspheric surfaces (see Japanese Patent Laid-Open Publication No. HEI 3-127008).
However, both systems have problems of their own; the first-mentioned zoom lens system which is solely composed of spherical surfaces uses too many lens elements to warrant commercial use and the second zoom lens system which uses many aspheric surfaces presents substantial difficulty in attaining balance between compactness (the overall lens length should be kept short) and efficiency for the correction of chromatic aberrations. As a further problem, either type of zoom lens system features a half view angle of only about 30.degree. at the wide-angle end, and it is desired to develop a system that has a wider coverage of viewing angles.